It is increasingly recognized that incentives can motivate behavior change and improve outcomes along the HIV care continuum. Under the right circumstances, financial incentives can increase the demand for HIV testing, change short-term sexual behavior, enhance linkage to care after HIV diagnosis, and promote antiretroviral therapy (ART) adherence. However, there are significant gaps in our understanding of the pathways through which incentives improve health, as well as whether they have unintended consequences and benefits. These knowledge gaps preclude definitive explanation of why incentives work in some programs but not others, and limit our understanding of which components to include in future programs. Understanding the mechanisms through which incentives change behavior and for whom they work best is essential in order to guide the scale-up of incentive-based programs in a variety of settings, including those targeting people living with HIV infection (PLHIV). We have the opportunity to address this knowledge gap by leveraging our ongoing study of short-term food and cash transfers for food insecure PLHIV in Shinyanga, Tanzania. This study includes food insecure PLHIV who are randomized to receive 6 months of food or cash transfers, conditional on clinic visit attendance, which is intended to reduce barriers to ART adherence and retention in care. The mixed-methods study proposed here explores unaddressed questions in the parent study and will use two complementary approaches in order to explore the pathways through which incentives operate. In Aim 1, we will conduct a qualitative study consisting of 32 in-depth interviews with PLHIV to explore the influence of personal, familial, and structural factors on the decision-making process of how food or cash assistance is utilized and how this influences adherence. In Aim 2, we will use quantitative survey data from 576 PLHIV to examine how food insecure PLHIV utilize food or cash assistance, whether there are unanticipated positive or negative outcomes, and whether the transfers' effect on adherence at 12 months is heterogeneous depending on the recipient's characteristics, such as motivation for being adherent and expectations about the future. At the conclusion of the research, we will have a better understanding of the mechanisms through which incentives may improve adherence to ART and retention in care. We will also know whether the incentives used in this setting had additional unintended benefits or adverse effects among PLHIV or their households. This timely information may be widely applicable to the spectrum of cash and in-kind assistance programs currently being designed, implemented, or under consideration to improve the health of PLHIV.